Conversion of liquid to solid tetrachlorobutane



July 10, 195l K. c. EBERLY ErAL 2,560,025

CONVERSION OF LIQUID TO SOLID TETRACHLOROBUTANE Filed Nov. 22, 1947 @Taz ried out continuously.

Patented July 10, 1951 UNITED STATES PATENT OFFICE CONVERSION OFLIQUID TO SOLID TETRACHLOROBUTAN E Kenneth C. Eherly, Akron, and Robert J. Reid, Canal Fulton, Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio Application November 22, 1947, Serial No. 787,504

6 Claims. (Cl. 260-658) This invention relates to a process for converting the liquid modification of 1,2,3,4tetrachloro butane to the solid modification thereof.

1,2,3,4-tetrachlorobutane (hereinafter designated tetrachlorobutane) contains two symmetrically disposed asymmetrical carbon atoms tion of a certain amount of the liquid modication is unavoidable. By the proper choice of conditions, catalysts etc., the yield of the solid modification may be increased. In practical operation, however, at least 3,0% of the tetrachlorobutanes obtained will usually consist of the liquid modiiication, which must be discarded or diverted to the manufacture of relatively less pure products.

Accordingly, it is an object of this invention to convert the liquid modification of tetrachlorobutane to the solid modification.

Another object is to convert the liquid modification to the solid by a process which may be carmay be carried out cyclically, the solid modification being separated from the reaction products and the liquid being recycled. The reaction is also more rapid in the higher temperature ranges. in which ranges, however, there come into play competing reactions such as cracking and carbonization. which result in a net loss of materials.

TEMPERATURE OF OPERATION As noted, the temperature of operationmay vary from 100l1 C. to 525 C. Below this range, the reaction becomes impractically slow, while above this range the loss of materials by way of cracking, polymerization, etc. is excessive.' Between these limits, the choice of temperature depends upon an economic balance of speed -of reaction and consequent charges for reactor space on the one hand and cost of lost material .on the other hand. The upper portion of the temperature range is also somewhat less desirable due to corrosion and fouling of the equipment A further object is to provide such a process which may be carried out expeditiously and economically in readily and cheaply procurable equipment, with a minimum of skilled super-v vision.

A still further object is to provide a catalytic process for converting the liquid modification of tetrachlorobutane to the solid modification.

SYNOPSIS OF THE INVENTION It has been discovered by this invention that the liquid modification of tetrachlorobutane, when'subjected in the vapor phase to temperatures in the range 100 C.-525 C., in the presence of a zinc chloride catalyst, becomes partly converted to the solid modification. The reaction appears to be one of equilibrium, slightly favoring the solid modiiication, and in order to increase the yield of solid modification, the process which sets in at these ranges. In general, the economically most advantageous temperatures lle betweenl50 C. and 250 C.

THE RATE' OF REACTION AND DWELL OF MATERIALS IN TI-TEI REACTION ZONE As noted above, the reaction to which the instant invention relates is reversible, and comes to an equilibrium in which the solid form of' tetrachlorobutane predominates to some extent. However, the order of the reaction appears to be such that, after more than about 25% of the liquid modification of tetrachlorobutane has been converted to the solid, further approach to the equilibrium conditions becomes unproiitably slow, particularly if conditions are sufficiently drastic that competing reactions such as carbonization and cracking are appreciable. In general, it will not be advantageous to press the reaction beyond a yield of about 25% of solid in a single treatment of the liquid modification feed stock. This yield corresponds to a minium feed of at least .0002 gram of liquid tetrachlorobutane per cubic centimeter of reaction space per hour. A feed of greater than .01 gram of liquid 'tetrachlorobutane per cubic centimeter of reaction space per hour will result in a rather low percentage of conversion.

The relatively low conversion obtained on a single pass of the feed stock may be offset, in accordance with this invention, by separating the liquid and solid modications from the product leaving the reaction Zone, and recycling the liquid modification back to the reaction zone.- The same result may be obtained by forwarding the unconverted liquid modication to a second conversion treatment zone, again separating the liquid from the solid modication, re-forwarding 4 diameter) borosilicate glass reaction tube l placed in an electric tube furnace I2, the heating zone being 69 cm. long. The charging end I4 is bent upwardly, and a dropping funnel I6 the unconverted liquid, and so on, limited only 5 fitted thereinto through a neoprene stopper I8. by the economic balance between recovery of The discharge end 2l)` is directed into a consolid modification and cost of the additional denser 22 and receiver 24. A vacuum connectreatments. Another limitaton on recycling and tion 25 is provided for maintaining the system retreatment of the unconverted liquid is the acunder a vacuum. A series of thermocouples 26 cumulation, in the system, of cracked products, l0 is provided for determining and regulating the and of impurities introduced with the initialfeed. r'temperatures at the various points along the This limitation can be overcome, to a considertube. able extent, by purging the impurities' from the A number of runs was made in this apparatus, recycled or re-treated liquid material. The sepusing various temperatures, rates of feed, and aration of the solid modication at each stage catalysts in the reaction tube l0. In each case, may be accomplished by freezing out, or by disthe temperature of the tube l0 Was adjusted to tillation. In general, recycling and/or forwardthe lvalue selected for that run, and the system ing of the liquid modification as above outlined evacuated to 100-150 mm. to facilitate vaporizamay be carried out protably to a degree such tion of the material fed. Substantially pure as to obtain a-60% overall yield of solid modica- 20 liquid modication of tetrachlorobutane, to the tion of tetrachlorobutane. On the basis of extent of 100 grams, was charged into the droplconversion in a single reaction stage, this is ping funnel IB and dropped into the tube l0 at equivalent to about 4 theoretical stages. the preselected rate, whereby it became vaporized in the tube I0, subjected to the heat prevailing CATALYSIS j therein, and discharged and condensed in the As above noted, the conversion of solid toliq'- condenser 22 and receiver 24. When all the mauid tetrachlorobutane is greatly accelerated by terial in the dropping funnel IG had been used the use of a zinc chloride catalyst, preferably up;the product collected at 24 was fractionally supported upon a porous carrier. If a carrier is distilled.v The fraction, if any, coming overbeused, it will be preferable to deposit Vthe vzinc low 130 C. at 100 mm. pressure was discarded chloride catalyst thereon (as by impregnation as consisting of cracked products. The rewith aqueous solution and drying) to the extent mainder, consisting of solid and liquid tetraof from .about 3% to about 40%, based on the chlorobutane, was redistilled through a column total Weight of carrier and zinc chloride. at 22 mm. pressure. The fraction coming over lWith the foregoing general discussion in mind, 35 at. .Q30-94.5 C. was `substantially pure liquid the .invention will now be described in detail tetrachlorobutane, and the residue was substanin connection with the attached drawings. in tially pure vsolid tetrachlorobutane. Set forth which: herewith in Table I are the particulars of the Fig. 1 showsan apparatus for demonstrating several runs.

Table I Reaction Conditions Condition Products (Percent of Material Charged) ses Flw Rate Tube at Lossesin sono Liquid sa 221 `.0042 97 3 1.7 1.7 94 v1 303 co1 es 32 o. o 5. 1 to 2 None 34o .0013 99 1 3. s 5. s ss 3 421 11013 97 3 7. e 11. 1 79 4 457 .noos s1 19 14. 2 17.3 49 5 523 :co1 4s 52 25. 9 4.1 s 23o .0013 91 (more s) 9 0.3 2.5 7 Silica. Gel (Note l) 300 .0011 93 (note 3) 7 2.0 7.0 8 ass .0913 72 (umana 8.5 11.9 9 9o 004-A s2 (none s) 1s 0.o 0.o 1o sincaoeiand 10% znct 194 .ooi e5 (note m14 n.4 19.1 11 (Nate 2) 233 .om 85 (note 3) 15 .5 17.7 12 281 .no1 so (note smo 4.o 5.4 1a

Norn 1. 86 grams of 6-20 mesh silica gel packed into heating section of the tube 10.

NOTE 2. 86 grams of (H0 mesh silica gel impregnated b y means oi an aqueous solution with 10% by Weight of the silica gel of zinc chloride thoroughly dried before use at 225 C. packed asin note l.

the variations of which the instant invention is capable, and Fig. 2 shows an arrangement for continuous production with recycling of the unconverted liquid modification.

In the description to follow, all parts given are by weight.

EXAB/IPLE I Variation of conditions and optimum values thereof A, The apparatus employed in this example is shown in Fig. 1 as comprising a 22 mm. (outside NOTE 3. The loss in these runs is due largely to hold-up in the catalyst mass at the end of the run.

From an inspection of Table I, it will be evident that, although the conversion reaction will take place in the absence of the catalyst of this 5 invention (runs Nos. 1-6) it is necessary to .12) Mere surface catalysis (runs Nos. 7-9) appears to have no effect. Results comparable to those of runs Nos. 11-13 were obtained with pum- `ice, diatomaceous earth, and active clays impregnated with from 5% to 50% of zinc chloride.

at pressures ranging from '75 mm. to 3 atmospheres, and over temperature ranges from 100C. to 450 C.

EXAMPLE II Continuous operation recycle of unconoerted tetrachlorobutane The equipment employed in this example is shown in Fig. 2 as comprising a supply tank 30 containing the liquid tetrachlorobutane to be converted to the solid form, which supply-tank feeds through a throttled line 3| into an evaporator 32 containing a heating coil 34 for vaporizing the liquid tetrachlorobutane into the rest of the system. The vaporized tetrachlorobutane passes through a line 36 to a series of three vertical steel reactor tubes 38, 6 inches in diameter and '7 feet tall connected in series. The tubes are packed as indicated at 40 with the silica gel catalyst referred to in note 2 of Table I, and are provided with electric heaters 42. The tubes are maintained at 220 C., 150 mm. pressure, and throughput is at the rate of .001 gram of tetrachlorobutane per c. c. of reaction space per hour-i. e., the conditions of item 12 of Table I are simulated as far as possible. Passage through the tubes 38 effects the conversion of about 15% of the liquid tetrachlorobutane to the solid modification. The tubes 38 discharge vapors of the mixed solid and liquid modication at 44 into the feed section of a reflux tower 45 packed with vertically disposed glass fibers and providing an equivalent of 20 plates above and below feed under the conditions of operation, the reflux ratio being 0.8:1 (reflux: vapors from top of tower), still head temperature being 132 C., still bottom 142 C., pressure at still head being 100 mm. The solid modification is discharged at the reboiler section 46, while the liquid modification passes out through a partial condenser 48 to the feed section of a stripper column 50. The stripper column is operated so as to purge out, as overhead, a quantity of materia1 equal to about 30% of the feed at 3|, thus continuously purging the system of cracked products and casual impurities along, of course, with an unavoidable loss of some tetrachlorobutane constituents. The liquid tetrachlorobutane discharged from the reboiler 52 is recycled at 54 to the vaporizer 32. In continuous operation, the above equipment effected between about 50% and about 65% conversion of the liquid tetrachlorobutane supplied at 30 to solid tetrachlorobutane.

Reference is made to the companion application of Eberly Ser. No. 787,505, filed November 22, 1947, drawn to the conversion process generally, independently of the presence or absence of catalysts.

What is claimed is:

1. Process which comprises heating the liquid modification of 1,2,3,4tetrachlorobutane at temperatures between 100 C. and 525 C., in the presence of a zinc chloride catalyst, whereby to convert a portion of the liquid modification of 1,2,3,4tetrachlorobutane to the solid modification, and separating the solid modification of 1,2,3,4-tetrachlorobutane from the resultant mixture.

2. Process which comprises heating the liquid modification of 1,2,3,4tetrachlorobutane attemperatures between 150 C. and 250 C., in the presence of a zinc chloride catalyst, whereby to convert aportion of the liquid modification of 1,2,3,4tetrachlorobutane to the solid modification, and separating the solid modification of 1,2,3,4tetrachlorobutane from the resultant mixture.

3. Process which comprises heating the liquid modification of 1,2,3,4-tetrachlorobutane at temperatures between C. and 525 C., in the presence of a zinc chloride catalyst, whereby to convert a portion of the liquid modification of 1,2,3,4tetrachlorobutane to the solid modification, separating the solid modification of 1,2,3,4 tetra-chlorobutane from the resultant mixture, heating the residual liquid niodication of 1,2,3,4 tetrachlorobutane at temperatures between 100 C. and 525 C. whereby to convert a further portion of the liquid modification of 1,2,3,4tetra chlorobutane to the solid modification, and separating the newly formed solid modification of 1,2,3,4-tetrachlorobutane from the -still unconverted liquid modification of 1,2,3,4tetrachloro butane. K 4. Continuous process of converting the liquid modification of 1,2,3A-tetrachlorobutane to the solid modification, which comprises passing the liquid modification through a reaction zone containing a zinc chloride catalyst maintained at from 100 C. to 525 C., whereby to convert a portion of the liquid modification to the solid modification, separating the solid modification from the resultant mixture, and recycling the residual liquid modification to said reaction zone.

5. Proces-s which comprises heating the liquid modification of 1,2,3,4-tetrachlorobutane at temperatures between C. and 250 C., in the 'presence of -a zinc chloride catalyst, whereby to convert a portion of the liquid modification of 1,2,3,4tetrachlorobutane to the solid modification, separating the solid modification of 1,2,3,4 tetrachlorobutane from the resultant mixture, heating the residual liquid modification of 1,2,3,4 tetrachlorobutane at temperatures between 150 C. and 250 C., in the presence of a zinc chloride catalyst, whereby to convert a further portion of the liquid modification of 1,2,3,4tetrachlorobu tane to the solid modification, and separating the newly formed solid modification of 1,2,3,4tetra chlorobutane from the still runconverted liquid modification of 1,2,3,4-tetrach1orobutane.

. 6. Continuous process of converting the liquid modification of 1,2,3,4l-tetrachlorobutane to the solid modification, which comprises passing the liquid modification through a reaction zone containing a zinc chloride catalyst maintained at from 150 C. and 250 C., whereby to convert a portion of the liquid modification to the solid modification, separating the solid .modification from the resultant mixture, and recycling the residual liquid modification to said reaction zone.

KENNETH C. EBERLY. ROBERT J. REID.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS pages 1545-8 (1932).

Backer et al.: Rec Trav. Chim. des Pays-Bas,

vol. 54, pages 52-6 (1935) Betti et al.: Atti X0 congr. intern. chim., vol.

2, pages 112-16 (1938). 

1. PROCESS WHICH COMPRISES HEATING THE LIQUID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE AT TEMPERATURES BETWEEN 100* C. AND 525* C., IN THE PRESENCE OF A ZINC CHLORIDE CATALYST, WHEREBY TO CONVERT A PORTION OF THE LIQUID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE TO THE SOLID MODIFICATION, AND SEPARATING THE SOLID MODIFICATION OF 1,2,3,4-TETRACHLOROBUTANE FROM THE RESULTANT MIXTURE. 